The Correlation Between Charge and Discharge Current for the Electrochemical Stability and Durability of Electrolyte in a Vanadium Redox Flow Battery

The object of this paper is to simulate electrochemical performances of V-electrolyte employed in the VRFB cell when different charge/discharge current densities are given. Experimental results show that increasing charge(or discharge) current for a given discharge (or charge) current leads to the reduction of both voltaic efficiency and charge(or discharge) capacity as compared to the use of same charge/discharge currents, while resulting in coulombic efficiency improvement. In contrast, the decreasing cases provide the improvement of both the voltaic efficiency and the capacity, but there takes place a serious problem of the capacity fading effect as well as the coulombic efficiency reduction. This is because low charge/discharge current densities causes polarization effects and self-discharges during cyclic operation, resulting in electrochemical instability of electrolyte performance. Consequently, both the charge and discharge current densities have to be employed over 80 mA/cm² to keep an electrochemical stability of electrolyte.